adj. not transmitting or reflecting light or radiant energy; impenetrable to sight

Etymologies

Middle English opake, shady, and French opaque, opaque (from Old French, shady), both from Latin opācus.

(American Heritage® Dictionary of the English Language, Fourth Edition)

From Middle English opake, from Latin opacus ("shaded, shady, dark") (of unknown origin), later reinforced from Middle French opaque. (Wiktionary)

Examples

And now my chains are to be broken; I shall mount above these clouds and opaque airs in which I live, opaque, though they seem transparent, and from the heaven of truth I shall see and comprehend my relations.

Pensions & Investment Research Consultants Ltd., or Pirc, recommends voting against the remuneration report, because of what it calls "opaque" disclosure and "overly complex" structure of executives' packages.

They have told us that our atmosphere is what they call opaque, so that the stars are not visible, and then they were surprised that we know stars, that we know their music and the movements of their dance far better than beings like you who spend hours studying them through what you call telescopes.

The value of such a discovery was obvious from the first; and was still further enhanced by the discovery made shortly that, photographic plates are affected by the rays, thus making it possible to make permanent photographic records of pictures through what we know as opaque substances.

The reception, to the rear of the ground floor hall space, is all white with one purple wall to create a slightly softer and more welcoming space than the daringly dark remainder of the scheme, with white desking and a giant mirror on the chimney breast; a contemporary take on a baroque frame in opaque acrylic.

"The book is constructed of sequentially numbered sheets of paper (recyclable), each capable of holding thousands of bits of information. The pages are locked together with a custom-fit device called a binder which keeps the sheets in their correct sequence. Opaque Paper Technology (OPT) allows manufacturers to use both sides of the sheet, doubling the information density and cutting costs. Experts are divided on the prospects for further increases in information density."- The Book.